/*********************************************************************************
 *                                                                               *
 * The MIT License (MIT)                                                         *
 *                                                                               *
 * Copyright (c) 2015-2022 aoju.org OSHI and other contributors.                 *
 *                                                                               *
 * Permission is hereby granted, free of charge, to any person obtaining a copy  *
 * of this software and associated documentation files (the "Software"), to deal *
 * in the Software without restriction, including without limitation the rights  *
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell     *
 * copies of the Software, and to permit persons to whom the Software is         *
 * furnished to do so, subject to the following conditions:                      *
 *                                                                               *
 * The above copyright notice and this permission notice shall be included in    *
 * all copies or substantial portions of the Software.                           *
 *                                                                               *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR    *
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,      *
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE   *
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER        *
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, *
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN     *
 * THE SOFTWARE.                                                                 *
 *                                                                               *
 ********************************************************************************/
package org.aoju.bus.health.unix.aix.drivers;

import org.aoju.bus.core.annotation.ThreadSafe;
import org.aoju.bus.health.Executor;

import java.time.LocalDateTime;
import java.time.ZoneId;
import java.time.format.DateTimeFormatter;
import java.time.format.DateTimeParseException;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * Utility to query logged in users.
 *
 * @author Kimi Liu
 * @version 6.5.0
 * @since Java 17+
 */
@ThreadSafe
public final class Who {

    // sample format:
    // system boot 2020-06-16 09:12
    private static final Pattern BOOT_FORMAT_AIX = Pattern.compile("\\D+(\\d{4}-\\d{2}-\\d{2})\\s+(\\d{2}:\\d{2}).*");
    private static final DateTimeFormatter BOOT_DATE_FORMAT_AIX = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm");

    /**
     * Query {@code who -b} to get boot time
     *
     * @return Boot time in milliseconds since the epoch
     */
    public static long queryBootTime() {
        String s = Executor.getFirstAnswer("who -b");
        if (s.isEmpty()) {
            s = Executor.getFirstAnswer("/usr/bin/who -b");
        }
        Matcher m = BOOT_FORMAT_AIX.matcher(s);
        if (m.matches()) {
            try {
                return LocalDateTime.parse(m.group(1) + " " + m.group(2), BOOT_DATE_FORMAT_AIX)
                        .atZone(ZoneId.systemDefault()).toInstant().toEpochMilli();
            } catch (DateTimeParseException | NullPointerException e) {
                // Shouldn't happen with regex matching
            }
        }
        return 0L;
    }

}
